1. Field of the Invention
The invention relates to a nuclear reactor installation with a small high temperature reactor. The core of the reactor comprises a pile of spherical fuel elements, with a cooling gas flowing through said core from bottom to top. The principal heat exchangers are arranged in the cooling gas circulation loop above the small high temperature reactor and housed together with the small high temperature reactor in a steel pressure vessel. At least two circulating blowers following the principal heat exchangers in the direction of flow of the cooling gas. The reactor has decay heat exchangers installed in the steel pressure vessel, each of said decay heat exchangers installed in the steel pressure vessel, each of said decay heat exchangers being connected to an external heat exchanger by a decay heat removal (NWA) water circulation loop in a geodetically higher location.
Small high temperature reactors, which are installed together with a heat utilization system (steam generator, tubular canned furnace, He/He heat exchanger) in a steel pressure vessel, different installations and processes have already been developed for the removal of decay heat.
2. Description of the Prior Art
West German Application No. P 33 45 113.3 describes a nuclear power station with a small high temperature reactor, in which the decay heat is removed by means of the operational steam generators from the primary loop. This process has the disadvantage that either the primary steam generators and blowers must have a very high availability or that in case of a failure of the primary steam generators and blowers, the installations in the reactor core are exposed to very high temperatures.
West German Application No. P 32 12 266 and West German Patent No. 31 41 892 shows to use an operational concrete cooling system for the removal of decay heat in case of a failure of the operating steam generators and/or blowers, said concrete cooling system being arranged inside a concrete safety jacket surrounding the steel pressure vessel and operated by natural circulation. The heat is transferred by radiation from the steel pressure vessel that is laid out largely without thermal insulation, to the concrete. In these two nuclear reactor plants a high degree of availability of the primary steam generators and blowers is required and high temperatures are generated on the reactor installations if these components fail.
In the nuclear reactor plant shown in West German Patent No. 32 28 422 with at least one small high temperature reactor, separate decay heat exchangers are placed in the primary loop. They are arranged together in the steel pressure vessel above the small high temperature reactor and connected in parallel with the principal heat exchangers. For each decay heat exchanger an auxiliary blower is provided in a location above it. On the cooling water side, each of the decay heat exchangers is connected through a NWA (decay heat removal) loop with a geodetically higher located recooling heat exchanger, which is installed outside a biological shield surrounding the steel pressure vessel. Each of the external recooling heat exchangers may be located in a shaft provided in the wall of the reactor protection building, the lower part filled with water is in the form of an evaporation chamber. The decay heat exchangers and the recooling heat exchangers associated with them are combined in a thermosiphon circulation. The removal of the decay heat is effected either by the evaporation of the water present in the evaporation chambers or by the transfer of heat to the external atmosphere flowing through the recooling heat exchangers and the shafts.